New technologies are being developed to increase the capacity and bandwidth of telecommunications networks. One of these new technologies provides for the use of an asymmetric digital subscriber line (ADSL) system in the local loop between a central office of a telecommunications network and a customer's premises served by that central office. An ADSL system makes use of the existing twisted pair wiring provided to the customer's premises to deliver the voice service including plain old telephone service (POTS) and to deliver data service including data signals such as may be used to communicate over the Internet. Advantageously, the ADSL system allows a customer to engage in a telephone call while also engaging in digital communications such as by interacting with the Internet.
Additional information regarding ADSL systems may be obtained from American National Standards Institute Standard ANSI-T1.413-1995, which is incorporated herein by reference.
FIG. 1 illustrates an ADSL system 10 such as may be used in a local loop between a customer's premises 12 and a central office 14 of a telecommunications network that serves the customer's premises 12. In the central office 14, voice signals from a switch 16 are combined with data signals from an ADSL modem 18. This combination of voice signals and data signals typically takes place in a splitter 20, which then transmits the combined signals over the twisted pair wiring 22 serving the customer's premises. The splitter 20 in the central office 14 earns its name when combined signals are received in the central office 14 from the customer's premises over the twisted pair wiring 22. The splitter 20 splits the combined signals into voice signals which are transmitted to the switch 16, and into data signals which are transmitted to the ADSL modem 18.
Referring again to the case where the splitter 20 in the central office 14 transmits the combined signals over the twisted pair wiring 22 serving the customer's premises 12, these combined signals are received at a splitter 24 in the customer's premises 12. This splitter 24 also earns its name by splitting the combined signals into voice signals and data signals. The voice signals are transmitted to the telecommunications devices 26 in the customer's premises 12, thereby providing voice service. The data signals are transmitted to the data devices in the customer's premises, thereby providing data services. For example, the splitter 24 provides data signals to an ADSL modem 28 which performs the appropriate demodulation and provides the demodulated data signals to a computer 30. The splitter 24 in the customer's premises also transmits combined signals from the customer's premises 12 to the central office 14. In particular, the splitter 24 receives voice signals from a telecommunications device 26 and combines these voice signals with data signals received from the computer 30 via the ADSL modem 28. The splitter 24 transmits the combined signals over the twisted pair wiring 22 to the central office 14. By this described configuration, the ADSL system 10 simultaneously provides a customer with voice service and data service so that a customer may use his or her computer 30 while he or she (or another individual) makes use of the telephone 26.
In the ADSL system 10 of FIG. 1, as noted, the splitter 24 in the customer's premises 12 is used substantially in two ways. First, the splitter 24 is used to split the combined voice and data signals transmitted from the central office 14 over the twisted pair wiring 22.
Second, the splitter 24 is used to combine the voice signals from the customer's telecommunications device 26 with the data signals of the customer's computer 30 and to transmit the combined voice and data signals over the twisted pair wiring 22 to the central office 14. Based on both of these uses, the splitter 24 must be installed on the customer's premises, which typically requires appropriate access and special wiring to make the proper connections. These requirements present problems to the telecommunications service provider and are viewed as complications by the customer. To the service provider, these requirements are costly and inconvenient. To the customer, these requirements of an ADSL system seem complex in comparison to the familiar use of an analog modem. Typically, a customer simply plugs the analog modem into a telecommunications outlet and programs the computer appropriately. To install an analog modem, generally special wiring and connections are unnecessary. Of course, an analog modem does not provide the advantage of an ADSL system whereby the customer may simultaneously use voice services and data services. Yet, the problems presented by the splitter 24 in the customer's premises 12 are obstacles to the further deployment of ADSL systems.
As illustrated in FIG. 2, to overcome the problems presented by the splitter 24 in the customer's premises 12, an ADSL system 32 without a splitter in the customer's premises 12 is currently being developed. Generally, such an ADSL system 32 includes ADSL modems that operate at lower power than the ADSL modems in an ADSL system 10 with a splitter in the customer's premises. Additional information regarding an ADSL system without a splitter in the customer's premises may be obtained from Universal ADSL Working Group, an industry consortium formed to develop Universal ADSL standards. Further information may be obtained also from the following documents which are incorporated herein by reference: U-ADSL Framework Document—Terms of Reference, Implementation Guide, Rev. 1.2 (Jun. 15, 1998), Universal ADSL Working Group; and U-ADSL Framework Document—Loop Plants, Impairments and Testing. In-Line Low-Pass Filter Requirements and Design Guide, Rev. 1.2 (Jun. 15, 1998).
A comparison of FIG. 2 to FIG. 1 reveals that in the central office 14 the configuration of the ADSL system 32 without a splitter is the same as the configuration of the ADSL system 10 with a splitter. The principal differences between the ADSL systems 10, 32 are in the customer's premises.
In the ADSL system 32 without a splitter, the combined voice and data signals transmitted over the twisted pair wiring 22 from the central office 14 are received in the customer's premises 12 and are provided to both the customer's telecommunications devices and to the customer's data devices. In particular, in providing the combined voice and data signals to the telecommunications devices, the combined signals are received in the customer's premises 12 and provided over connection 34 to an optional low pass filter (LPF) 36 which is connected in series to the customer's telecommunications device 26. The low pass filter 36 passes the voice signals (0-4 KHz) to the telecommunications device 26, but significantly blocks the other signals. In providing the combined voice and data signals to the data devices, the combined signals are received in the customer's premises 12 and provided over connection 38 to a high pass filter (HPF) 38 which is connected in series to the ADSL modem 28. The high pass filter 38 passes the data signals (above 20 KHz) to the ADSL modem 28, but blocks the other signals. The ADSL modem 28, in turn, then transmits the data signals to the computer 30.
The ADSL system 32 illustrated in FIG. 2 has done away with the problems of a splitter 24 in the customer's premises. But the ADSL system 32 without a splitter in the customer's premises 12 has its own set of problems. Principally, these problems concern the degradations in the respective voice services and data services that occur when both services are in use. For example, consider the experience of a customer having the ADSL system 32 for the delivery of voice service and data service. When the customer is using his or her computer 30 and receiving data service through the ADSL system 32, the customer may experience a degradation in the data service if the telecommunications device 26 connected to the ADSL system 32 is used so that voice service use at the same time as the data service. The degradation in the data service generally includes a slow down in the delivery of the data. On the other hand, when the customer is engaged in a telephone call and using the voice service, the customer may experience a degradation in the voice service if the computer 30 is used so that data service is operated at the same time as the voice service. The degradation in the voice service generally includes audible noise such as a hum that may be heard through the receiver of the telecommunications device. In sum, degradations may occur in both services when they are used at the same time.
These degradations in the data service and the voice service are partially the result of harmonic noise. In addition, the degradations may be generally attributable to the effects of the wiring, connections and other devices that may be present in or relatively near the customer's premises or may be connected at the customer's premises 12 to the ADSL system 32. Thus, the degradations in the data service and in the voice service are likely to vary from customer to customer.
As noted, in addition to providing high data rate access using the local loop, a principal advantage of an ADSL system is that it allows a customer to make use of his or her telecommunications devices and data devices at the same time. As also noted, a problem of an ADSL system is the degradation that may occur to one or both of the services supplied by the ADSL system when the services are used at the same time. In some cases, the advantage of being able to use both voice services and data services at the same time may outweigh any problem caused by the degradations. For example, a customer who is engaged in a social call with a friend may tolerate the degradation in the audio quality of the telephone call so as to browse the Internet at the same time as talking to his or her friend. As another example, a customer who is browsing the Internet for fun and entertainment may tolerate the degradation in the data service such as a data slow down when at the same time the customer's daughter or son uses the telephone to call a friend for help with school work.
Nevertheless, there are other cases when the advantage of being able to use voice devices and data devices at the same time may be outweighed by the degradations that are caused by the simultaneous use of both services. For example, the customer who may tolerate the degradation in the audio quality when engaged in a social call may not be able to tolerate the degradation when engaged in a business call. As a result, the customer may have to forego malting or receiving business calls through his or her ADSL system. As another example, the customer who may tolerate the degradation in the data service when using it for fin and entertainment may not tolerate the degradation when the data service is being used for business. As a result, the customer may have to forego using the data service for business purposes when the voice service is being used. In either case, even though the customer may be able to tolerate degradations to either the voice service or data service in certain cases, the customer may have to completely forego simultaneous use of the services because the customer cannot tolerate degradations in all cases.
In sum, there is a need in an ADSL system 32 whereby a customer may be provided with options with respect to the use of an ADSL system such that the customer may choose to use or not to use data service and voice service at the same time, or may choose to operate or use one or the other of the services in a mode that is selected with consideration of the impact of the concurrent use of the services.